21612533 has 4 divisors (see below), whose sum is σ = 21623628. Its totient is φ = 21601440.

The previous prime is 21612529. The next prime is 21612581. The reversal of 21612533 is 33521612.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 2093809 + 19518724 = 1447^2 + 4418^2 .

It is a cyclic number.

It is not a de Polignac number, because 21612533 - 2² = 21612529 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21612499 and 21612508.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21612133) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1766 + ... + 6807.

It is an arithmetic number, because the mean of its divisors is an integer number (5405907).

Almost surely, 2^21612533 is an apocalyptic number.

It is an amenable number.

21612533 is a deficient number, since it is larger than the sum of its proper divisors (11095).

21612533 is an equidigital number, since it uses as much as digits as its factorization.

21612533 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11094.

The product of its digits is 1080, while the sum is 23.

The square root of 21612533 is about 4648.9281560377. The cubic root of 21612533 is about 278.5491835216.

The spelling of 21612533 in words is "twenty-one million, six hundred twelve thousand, five hundred thirty-three".